GB2193936A - Electrically assisted pedal vehicle - Google Patents

Abstract

A drive mechanism for power assistance of a pedal vehicle such as a tricycle for a handicapped child includes a conventional pedal (3), sprocket (1), chain (4) and freewheel sprocket (5) system. To this is added an electrical drive system including a further freewheel sprocket (8) driven by a chain (9) from an electric motor (11). The motor is energised by a switch (14) which is activated only when pressure is exerted on the pedals (3) so as to tension the chain. This tension results in movement of a follower (17) mounted on a pivotal arm (18), to activate the switch. The arm (18) is biassed adjustably in the opposite direction by means of a spring (20). Thus electrical assistance is brought in only whilst pedalling takes place. The electrical circuit may include a master switch (12) and a 12v battery (13) which may be recharged from the mains. <IMAGE>

Description

SPECIFICATION Electrically assisted pedal vehicle This invention relates to an electrically assisted pedal vehicle. The invention is particularly concerned with a pedal tricycle but could apply equally well to a bicycle, pedal car, gocart or the like.

This invention has been designed particularly with a view to assisting handicapped children who may find it difficult to pedal a tricycle under their own power alone. One aim of the particular design which has been developed is to encourage a child to pedal even though electrical power assistance is employed. There are known pedal vehicles which have an electrical drive system but it is possible to rely upon the electrical system alone, using the pedals only when the system cannot develop sufficient power. Not only does this fail to encourage pedailing to a sufficient degree, but the rider will have the psychological disadvantage of feeling that the vehicle is powered rather than being pedalled.This can be significant in the case of a handicapped child who may wish to pedal, e.g. a tricycle, like other chldren rather than be propelled by something similar to a motorised wheelchair.

Viewed from one broad aspect there is disclosed herein a pedal powered vehicle including means responsive to motive force being applied to a pedal by a rider so as to activate electrical power assitance. Thus, as the rider starts to pedal, power assistance is brought in and will continue until the rider ceases to pedal. It will generally be desirable to arrange the system so that the power assistance only operates above a threshold force applied to the pedal. This may prevent unintentional power assistance moving the vehicle when it is intended to be stationary and/or may provide for rider powered movement only, up to certain speeds or load conditions. Means may be provided to vary this threshold so as to accommodate different riders or to account for a rider becoming tired.Similarly, the electrical power assistance could be provided with a secondary activating circuit to permit powered movement without pedalling e.g. if a rider becomes too tired, or if the vehicle is to be used by a handicapped child unable to pedal for some reason.

The vehicle could be operable by a pair of pedals in the normal way, either by hand or by foot. It could also be designed to be operable by a single pedal only, again either by hand or by foot. The pedal drive could be direct to a drive wheel, e.g. as in front wheel driven infants' tricycles, or indirect by means of a mechanical linkage, e.g. as in a pedal car, or more usually by means of a chain and sprocket arrangement. The power assistance could be applied to the pedal driven wheel(s) or to any other wheel(s) as desired.

Because of its particular advantages for handicapped children, who may have stability problems, the vehicle preferably has three or four wheels. However, it may be possible to use a bicycle, perhaps with stabilising wheels at least initially.

A number of means may be employed for sensing the application of motive force by a rider, such as torque sensors or motion sensors. However, a particularly advantageous system has been devised for use with a sprocket and chain pedal drive mechanism.

Thus, viewed from another broad aspect, there is disclosed herein a pedal vehicle drive mechanism including a pedal driven sprocket and a wheel driving sprocket interconnected by a chain, wherein means are provided which are responsive to tension in the chain so as to activate an electrical drive system for the vehicle when the pedal mechanism is operated.

The tension responsive means may he in the form of a follower to be in contact with the chain. As torque is applied to the pedal driven sprocket part of the chain will be put into tension and slack will be taken up. This will cause movement of the follower and this can be arranged to cause activation of a switch for the electrical drive system. The follower could be part of the switch, or be in contact with, or be moved into contact with the switch, or operate the switch by means of another member.

The follower may be mounted in a guide for sliding movement or, more preferably, on a pivotal arm. Movement of the follower may be against the action of a biassing means such as a tension or compression spring. Means may be provided to vary the biassing force so as to adjust the chain tension at which the switch will be actuated. This will accordingly vary the degree of rider effort required before the electrical system comes into operation.

The follower may be in the form of an -idler sprocket, a rotatable roller, a fixed member made of or coated with a wear resistant low friction material such as nylon or PTFE, a fixed member made of hard wood, or in any other suitable form.

The electrical drive system will include a motor and this can drive a wheel by any suitable means, e.g. by a chain and sprocket mechanism. In the case of a tricycle, two sprockets may be provided on an axle carrying the rear wheels, one connected by a chain to the pedal mechanism and one by a chain to the electric motor. A suitable power source will be provided such as a rechargeable battery, and a master on/off switch may be provided also. The chain tension reponsive switch may be directly in the circuit supplying the motor or may be in a separate control circuit.

More complex arrangements may be envisaged. For example, the tension reponsive means could be fixed in position and be re sponsive to pressure caused by the chain when under tension. Thus a strain gauge, or the like, and suitable control circuitry could be used. Similarly the means could respond to increasing tension, so as to vary the power provided by the electric motor. This could be achieved by use of the strain gauge or like system mentioned above, or by a movable follower connected e.g. to a potentiometer. A dial or the like could be provided for presetting the tension at which power assistance would be provided, for adjusting the minimum or maximum assistance and so forth.

However, it is much preferred that a simple, inexpensive system be provided which is also capable of easy adjustment and repair. Thus, a simple follower and switch arrangement is preferred. Even so, a separate control may be desirable to enable the power output of the motor to be controlled so as to cope with inexperienced riders.

The particularly preferred vehicle for a handicapped child is a tricycle and this may incorporate other features to assist use by the child. Thus support may be provided for the child, with an optional harness, belt or the like to assist location on the saddle. At the rear at least one limiting bar may project backwards and downwardly to restrict the amount to which the tricycle can tilt. This will be a safety feature if the rider happens to ride up a bank or the like of excessive incline. The normal freewheel may be locked, permanently or releasably. This will assist in teaching the child how to pedal, by pushing the tricyle or even by powering it by the electric motor by using a separate activating system such as an overide on/off switch and if desired a remote control. The pedals may be adapted by making then larger and/or by using locating straps or the like.

Preferably, the electrical drive system may be provided in the form of a kit for modifying an existing pedal vehicle. In the case of the particularly preferred system described such a kit may be considered from one broad aspect as comprising an electric motor, means for attaching the motor to a vehicle, means for transmitting drive from the motor to a wheel of the vehicle, a power source, a switch for energising the motor from the power source, a follower for engagement with a pedal driven chain of the vehicle, and means for mounting the follower so as to be movable upon the chain being tensioned whereby to activate the switch.

It will be appreciated that many variations may be possible both to the broad aspects highlighted and to the specific features disclosed herein.

By way of example only, reference will now be made to a preferred system which embodies some of the features mentioned above, as descrihed below with reference to the accompanying drawing which is a schematic view of the drive system for a tricycle.

As shown, the pedal drive includes a drive sprocket 1 mounted for rotation on a tricycle frame, provided with cranks 2 having pedals 3 in the conventional manner. A chain 4 of a conventional type links the drive sprocket 1 to a driven sprocket 5 connected by means of a freewheel mechanism 6 to the rear axle 7 carrying the two rear wheels of the tricycle.

Also mounted on the rear axle 7, by means of a second freewheel mechanism, is a second sprocket 8 connected by a chain 9 to a sprocket 10 driven by an electric motor 11 fixed on the frame of the tricycle. The electric motor is connected in- series with a master switch 12, a rechargable 12v battery 13 and a microswitch 14. The battery 13 is provided with a recharging unit 15 which can be connected directly to a mains electricity supply by means of a socket 16.

The microswitch is arranged on the tricycle frame above a chain follower 17 of nylon which is provided at one end of an arm 18 mounted pivotally on the frame at 19. The arm is biassed downwardly by means of a tension spring 20 which has one end fixed to the arm and the other end selectively locatable at one of a number of anchor points 21 on the frame of the tricycle by means of a bolt or the like, The follower 17 is thus biassed into contact with the upper run of chain 4. In the rest position as shown, this means that microswitch 14 is open and the electric motor 11 is not powered.

When pressure is exerted by a rider on the pedals 3 to rotate the sprocket 1 in the direction of arrow A, so as to drive the tricycle forwards, the upper run of the chain 4 between sprockets 1 and 5 is placed under tension and straightens out. This causes follower 17 to pivot in the direction of arrow B, against the action of spring 20, to act on and close switch 14. Providing the main switch has been closed, the electric motor will be energised and will drive the rear wheels via sprocket 8. When pedalling stops the motor ceases to be energised.

In a preferred embodiment, the arrangement is such that the motor operates after a pedal force of about 15-20N is applied.

The required motor output will depend on a number of factors and the motor preferably includes a reduction gear. Satisfactory results have been obtained using an automobile windscreen wiper motor with a power output of aproximately 60-100W.

To enable easy conversion of an existing tricycle, the motor components are mounted on a plate for attachment to the tricycle frame. The microswitch 14 and the spring anchor points 21 are provided on a plate held in place by a screw in slot arrangement so as to permit adjustment.

In operation of the preferred embodiment described, the minimum speed of the motor is not governed by the speed of the pedals, due to the freewheel on the pedal system. If the sprocket 5 is turning more slowly than the sprocket 8, then the freewheel 6 will operate, If no freewheel was provided, then the speed of the motor would be governed by the speed of rotation of sprocket 5. Some motors will be able to cope with this, whilst others might require a slipping clutch mechanism or the like to prevent damage. If the sprocket 5 turns faster than the sprocket 8 driven by the motor, then the second freewheel will operate.

However, it may be that over running of the motor will not cause damage and that no second freewheel is necessary.

In conclusion, there has been described specifically a simple, inexpensive mechanism which will enable a physically handicapped child to pedal a tricycle or the like when normally the pedalling effort would be too great.

The arrangement embodies a number of advantageous features, both viewed specifically and from broad aspects. It will be appreciated that variations will be possible to these features and aspects whilst retaining at least some of the advantages. Protection is sought for all of the novel features diclosed herein, alone or in combinantion, and in the context of the particular mechanism and application disclosed as well as in other contexts such as drive mechanisms, ioad sensors, switch mechanisms and so forth generally. Furthermore, mention has been made of certain other improvements in relation to tricycles and the like, such as limiting bars, rider supports and so forth, and protection may be sought for these also. In general, those reading this specification must assume that protection may be sought in the broadest terms for all the features disclosed and for developments of them.

Any claim which may be appended hereto or which may otherwise be based on this disclosure are to be taken only as indicating the particular features in respect of which protection is sought for the time being.

Claims (18)

1. A pedal powered vehicle including means responsive to motive force being applied to a pedal by a rider, so as to activate electrical power assistance.

2. A vehicle as claimed in claim 1, wherein the electrical power assistance operates only when the rider applied force is above a predetermined minimum level.

3. A vehicle as claimed in claim 2, wherein the predetermined minimum level is variable.

4. A vehicle drive mechanism including a pedal mechanism comprising a pedal driven sprocket and a wheel driving sprocket interconnected by a chain, wherein means are provided which are responsive to tension in the chain so as to activate an electrical drive system for the vehicle when the pedal mechanism is operated.

5. A drive mechanism as claimed in claim 4, wherein the tension responsive means includes a follower to be in contact with the chain, movement of the follower in accordance with an increase in tension in the chain being arranged to activate a switch in the electrical drive system.

6. A drive mechanism as claimed in claim 5, wherein the follower is mounted at one end of a pivotal arm.

7. A drive mechanism as claimed in claim 5 or 6 including means for biassing the follower in a direction opposite to that in which it moves with increasing tension in the chain.

8. A drive mechanism as claimed in claim 7 including means for adjusting the biassing force.

9. A drive mechanism as claimed in any of claims 4 to 8, wherein the electrical drive system includes an electric motor arranged to drive a wheel by means of a freewheel mechanism.

10. A drive mechanism as claimed in any of claims 4 to 9, wherein the wheel driving sprocket of the pedal mechanism is arranged to drive a wheel by means of a freewheel mechanism.

11. An electrical drive mechanism for attachment to a pedal powered vehicle including a pedal driven chain, comprising a electric motor, means for attaching the motor to the vehicle, means for transmitting drive from the motor to a wheel of the vehicle, a power source, a switch for energising the motor from the power source, a follower for engagement with the pedal driven chain of the vehicle, and means for mounting the follower on the vehicle so as to be moveable upon the chain being tensioned whereby to activate the switch and energise the motor.

12. A mechanism as claimed in claim 11, wherein the follower is mounted at one end of a pivotal arm.

13. A mechanism as claimed n claim 11 or 12 including a spring for biassing the follower away from the switch activating position.

14. A mechanism as claimed in claim 13 including means for pre-adjusting the spring force.

15. A mechanism as claimed in any of claims 11 to 14, wherein the means for transmitting drive from the motor to the wheel includes a chain and a sprocket provided with a freewheel mechanism.

1 6. A pedal powered vehicle including a drive mechanism as claimed in any of claims 4 to 15.

17. A vehicle as claimed in claim 1, 2, 3 or 16, in the form of a cycle.

18. A vehicle as claimed in claim 17, in the form of a tricycle.